A different approach to theories with non-linear realization of supersymmetry was recently proposed by Dall'Agata et al [1]}. The authors of [1]} made their own attempt to derive the theory of a nilpotent superfield starting from a theory with linearly realized supersymmetry and with two unconstrained superfields. Their model suffers from a vacuum instability due to a tachyonic mass squared for the scalars. This result was interpreted in [1]} as goldstino condensation and as a vacuum instability in theories with non-linear realization of supersymmetry.
